Research Scholar
Promod Pillai, Department of Neurological Surgery
Mario Ammirati, Faculty advisor
Steffen Sammet, Co-Researcher
Biography
I am Promod Pillai, native of Kerala, India, pursued my medical education at Kottayam Medical College and was awarded with MBBS degree from Mahatma Gandhi University. I completed my neurosurgery residency training at NIMHANS Bangalore. My doctoral dissertation was on neurooncology involving metabolic characterization of gliomas with NMR spectroscopy, and I was awarded with Magister Chirurgiae (M.Ch). After completing a year of chief residency, I joined the faculty of Neurological Surgery at Amrita Vishwa Vidyapeetham University. I am most interested in image-guided neurosurgery, neuro-oncology, and minimally invasive skull base surgery and came to the United States to seek training in those areas in particular. I have also finished fellowship training in Radiosurgery and Steretactic Neurosurgery at University of Pittsburgh.
What is the issue or problem addressed in your research?
Although frameless stereotactic techniques have become indispensable in neurosurgery, their technical complexity requires careful definition and evaluation. Navigation is of particular concern when it is applied to approach a complex, tight surgical area like the temporal bone, where virtually every millimeter is important. Theoretically, the temporal bone is an ideal location in which to employ image-guided navigation because its bony construct precludes pre-operative and intraoperative shift. In this context, the feasibility of using a navigational system is determined by the system's accuracy and by the spatial characteristics of the targets. Literature addressing the accuracy of image guidance techniques in temporal bone surgery is relatively sparse. Accuracy of these systems within the temporal bone is still under investigation
We investigated the application accuracy of computed tomography (CT)-based, frameless, image-guided navigation to identify various bony structures in the temporal bone via a retrosigmoid approach
What methodology did you use in your research?
In a total of 10 operations, we performed a retrosigmoid approach simulating operative conditions on either side of 5 whole, fresh cadaveric heads. Six titanium microscrews were implanted prior to the surgical procedure around the planned craniotomy site as permanent bone reference markers. High-resolution CT scans were obtained (slice thickness, 0.6 mm, contiguous non-overlapping slices; gantry setting, 0 degrees; scan window diameter, 225 mm; pixel size, > 0.44 × 0.44). We used a Stryker® navigation system (Kalamazoo, MI) for intraoperative navigation. External and internal targets were selected for calculation of navigation accuracy.
What are the purpose/rationale and implications of your research?
The system calculated the target registration error to be 0.48 ± 0.21 mm, and the global accuracies (navigation accuracies) were calculated using external over-the-skull and internal targets within the temporal bone. Navigation accuracy overall was 0.91 ± 0.28 mm; for reaching internal targets within temporal bone , 0.94 ± 0.22 mm; and for external targets, 0.83 ± 0.11 mm. Ninety five percent of targets could be reached within 1.4 mm of the actual targets.
Using high-resolution CT and bone-implanted reference markers, frameless navigation can be as accurate as frame-based stereotaxy in providing a guide to maximize safe surgical approaches to the temporal bone. Though error-free navigation is not possible with the submillimetric accuracy required by direct anatomic contouring of tiny structures within the temporal bone, it still provides a road map to maximize safe surgical exposure. Computer-assisted technologies cannot replace good neuroanatomical knowledge for individually tailoring treatment strategy. Continued research and development in the field of navigational technology is necessary for its optimal use in the complex surgery of the temporal bone.
